1. Field of the Invention
This invention relates to a method of recognizing an obstacle to a vehicle. In addition, this invention relates to an apparatus for recognizing an obstacle to a vehicle. Furthermore, this invention relates to a recording medium which stores a computer program for recognizing an obstacle to a vehicle.
2. Description of the Related Art
A known obstacle recognition apparatus for a vehicle emits a forward wave beam such as a light beam or a millimeter wave beam into a given detection area in front of the body of the vehicle. In the case where an obstacle exists in the detection area, the forward wave beam encounters the obstacle before being at least partially reflected thereby. A portion of the reflected wave beam returns to the apparatus as an echo wave beam. The apparatus detects the obstacle in response to the echo wave beam.
The known obstacle recognition apparatus is used in a warning system for a vehicle which alarms when an obstacle such as a preceding vehicle exists in a given detection area in front of the present vehicle. The known obstacle recognition apparatus is used also in a system for a vehicle which controls the speed of the vehicle to maintain a proper distance between the vehicle and a preceding vehicle.
The known obstacle recognition apparatus additionally has the function of determining whether or not the detected obstacle is a preceding vehicle. It is important to discriminate a preceding vehicle from other objects such as road-side objects or delineators.
Japanese patent application publication number 6-59038 discloses a laser radar for a vehicle which detects objects in a given detection area in front of the vehicle. The laser radar in Japanese application 6-59038 determines whether or not detected neighboring objects are road-side reflectors (delineators). Specifically, detected neighboring objects are recognized as delineators when the following conditions 1), 2), and 3) are satisfied. 1) The heights of detected neighboring objects from a horizontal reference line (for example, the road surface) are approximately equal to each other. 2) The horizontal intervals between detected neighboring objects are approximately equal to each other. 3) The differences between the distances to detected neighboring objects are approximately equal to each other. In addition, the laser radar in Japanese application 6-59038 determines whether or not two detected objects correspond to a vehicle (for example, a preceding vehicle or a stationary vehicle). This determination is based on the fact that the rear end face of a vehicle has a pair of reflex reflectors. Specifically, two detected objects are recognized as corresponding to a vehicle when the following conditions 4), 5), and 6) are satisfied. 4) The distances to two detected objects are approximately equal to each other. 5) The heights of two detected objects from the road surface are approximately equal to each other, and are in a predetermined range. 6) The horizontal distance between two detected objects is equal to or less than about 3 m.
In the case where the present vehicle is travelling along a road having a varying slope (for example, the present vehicle reaches the beginning or the end of a sloping road), the detected heights of delineators differ from each other so that the previously-indicated condition 1) is not satisfied. Therefore, in this case, the laser radar in Japanese application 6-59038 can not recognize delineators. Furthermore, the laser radar in Japanese application 6-59038 can not detect delineators on the road surface which are called cat""s-eyes. As previously mentioned, the laser radar in Japanese application 6-59038 implements the determination as to a preceding vehicle on the basis of the fact that the rear end face of a vehicle has a pair of reflex reflectors. Accordingly, a two-wheeler or a motorcycle having a single reflector at its rear end can not be recognized as a preceding vehicle.
U.S. Pat. No. 6,018,308 (corresponding to Japanese patent application publication number 11-38142) discloses an obstacle recognition system for an automotive vehicle which is designed to distinguish preceding vehicles from other objects. The system in U.S. Pat. No. 6,018,308 includes a radar unit and a preceding vehicle determining circuit. The radar unit receives a signal produced by reflection of at least one of transmitted radar signals from an obstacle present in a given obstacle detectable zone, and determines a distance to the obstacle and a horizontal and a vertical angle of the obstacle from a preselected reference direction. The preceding vehicle determining circuit includes a two-dimensional shape data producing circuit that produces two-dimensional shape data of the obstacle on a two-dimensional plane in a width-wise and a vertical direction of the present vehicle based on the distance and the horizontal and vertical angles. The preceding vehicle determining circuit also includes a non-vehicle determining circuit that determines the obstacle as an object other than the vehicle when the two-dimensional shape data of the obstacle lies out of an ordinary vehicle shape range.
In the system of U.S. Pat. No. 6,018,308, the non-vehicle determination is responsive to a variation in the height of the obstacle which occurs for a prescribed time interval. The design enables the non-vehicle determination to be accurate even in the case where the present vehicle is traveling along a road having a varying slope.
U.S. Pat. No. 5,604,580 (corresponding to Japanese patent application publication number 7-225276) discloses a vehicular optical radar apparatus which can identify various types of obstacles as well as a preceding vehicle, thereby ensuring a reliable identification of the preceding vehicle running in the same lane as with a subject vehicle on which the apparatus is installed. In the apparatus of U.S. Pat. No. 5,604,580, light is emitted from a light emitting device. A scanner enables an area ahead of the subject vehicle to be scanned by the emitted light. A light receiving device receives the light caused by reflection of the emitted light at an object. A received-light intensity detection device detects an intensity of the reflected light received by the light receiving device. An obstacle identifying device identifies the object according to the distribution pattern of the received-light intensity detected by the intensity detection device, such as a pattern being obtained with respect to the scanning direction.
Japanese patent application publication number 10-142336 discloses an apparatus for recognizing a lane along which a vehicle is traveling. The apparatus in Japanese application 10-142336 calculates quantities xcex94x, xcex94y, and xcex94xcfx86 of movement of the vehicle which occur for every predetermined time interval on the basis of the speed V and the steering angle xcex8H of the vehicle. Here, xcex94x, xcex94y, and xcex94xcfx86 denote the quantity of movement in the lateral direction, the quantity of movement in the longitudinal direction, and the quantity of movement in the angular direction with respect to the vehicle, respectively. The apparatus in Japanese application 10-142336 includes a forward object recognizing section having a laser radar. The forward object recognizing section feeds a stationary-object determining section with information representing the positions of detected objects relative to the vehicle. The stationary-object determining section detects delineators on the road sides in response to the calculated vehicle movement quantities xcex94x, xcex94y, and xcex94xcfx86 and the information fed from the forward object recognizing section. The stationary-object determining section feeds a stationary-object-row recognizing section with information representing the detected delineators. The stationary-object-row recognizing section recognizes a row of delineators on the basis of the information fed from the stationary-object determining section. The stationary-object-row recognizing section feeds a lane estimating section with information representing the recognized delineator row. The lane estimating section estimates a lane along which the vehicle is traveling on the basis of the information fed from the stationary-object-row recognizing section. The estimated lane is used in determining a preceding vehicle. Specifically, a preceding vehicle to be detected is traveling along the lane same as the estimated lane.
It is a first object of this invention to provide a method of recognizing an obstacle to a vehicle which can discriminate a delineator group on the road surface and a nearby two-wheeler from each other at an early stage.
It is a second object of this invention to provide an apparatus for recognizing an obstacle to a vehicle which can discriminate a delineator group on the road surface and a nearby two-wheeler from each other at an early stage.
It is a third object of this invention to provide a recording medium which stores a computer program for recognizing an obstacle to a vehicle which can discriminate a delineator group on the road surface and a nearby two-wheeler from each other at an early stage.
A first aspect of this invention provides a method of recognizing an obstacle to a vehicle. The method comprises the steps of detecting height-wise positions of objects on the basis of distances to the objects from the vehicle, angles of the objects in a width-wise direction of the vehicle, and angles of the objects in a height-wise direction of the vehicle; determining a plurality of objects, which satisfy conditions predetermined depending on physical characteristics of delineators, to be objects composing a delineator group; when the detected height-wise position of an object in the delineator group which is nearest to the vehicle corresponds to a predetermined value or less, determining the delineator group to be a delineator group on a road surface; and determining whether or not each object in the on-road-surface delineator group is a non-delineator in response to conditions of the detected height-wise positions of the objects in the on-road-surface delineator group.
A second aspect of this invention provides an apparatus for recognizing an obstacle to a vehicle. The apparatus comprises radar means for applying a transmission wave to a predetermined angular range in a width-wise direction of the vehicle and a predetermined angular range in a height-wise direction of the vehicle, and detecting distances to objects, angles of the objects in the width-wise direction of the vehicle, and angles of the objects in the height-wise direction of the vehicle on the basis of reflected waves which result from reflections of the transmission wave; and recognizing means for recognizing obstacles ahead of the vehicle on the basis of the distances to the objects, the angles of the objects in the width-wise direction of the vehicle, and the angles of the objects in the height-wise direction of the vehicle which are detected by the radar means. The recognizing means comprises 1) object recognizing means for detecting height-wise positions of the objects on the basis of the distances to the objects, the angles of the objects in the width-wise direction of the vehicle, and the angles of the objects in the height-wise direction of the vehicle which are detected by the radar means; 2) delineator-group determining means for determining ones among the objects, which satisfy conditions predetermined depending on physical characteristics of delineators, to be objects composing a delineator group; 3) on-road-surface delineator-group determining means for, when the detected height-wise position of an object in the delineator group which is nearest to the vehicle corresponds to a predetermined value or less, determining the delineator group to be a delineator group on a road surface; and 4) non-delineator determining means for determining whether or not each object in the on-road-surface delineator group is a non-delineator in response to conditions of the detected heightwise positions of the objects in the on-road-surface delineator group.
A third aspect of this invention is based on the second aspect thereof, and provides an apparatus wherein the conditions predetermined depending on the physical characteristics of delineators are that intervals between the objects are smaller than a reference value.
A fourth aspect of this invention is based on the second aspect thereof, and provides an apparatus wherein the conditions of the detected height-wise positions of the objects comprise conditions of a variation in the detected height-wise positions of the objects.
A fifth aspect of this invention is based on the fourth aspect thereof, and provides an apparatus wherein the non-delineator determining means comprising means for determining whether or not each object in the on-road-surface delineator group is a non-delineator in response to a position of occurrence of a change among an increase, a decrease, and a constancy in a sequence of the detected height-wise positions of the objects.
A sixth aspect of this invention is based on the fifth aspect thereof, and provides an apparatus wherein the object determined to be the non-delineator is at a place immediately rearward of a position of occurrence of a change from an increase to a decrease in the sequence of the detected height-wise positions of the objects as viewed along a direction away from the vehicle.
A seventh aspect of this invention is based on the fifth aspect thereof, and provides an apparatus wherein the object determined to be the non-delineator is at a place immediately rearward of a position of occurrence of a change from a decrease to an increase in the sequence of the detected height-wise positions of the objects as viewed along a direction away from the vehicle.
An eighth aspect of this invention is based on the sixth aspect thereof, and provides an apparatus wherein the height-wise position of the object determined to be the non-delineator corresponds to a prescribed height or greater.
A ninth aspect of this invention is based on the eighth aspect thereof, and provides an apparatus wherein the prescribed height depends on a distance from the present vehicle.
A tenth aspect of this invention is based on the second aspect thereof, and provides an apparatus wherein the object recognizing means comprises means for recognizing shapes of the objects, and the delineator-group determining means comprises means for determining ones among the objects to be objects composing a delineator group in response to the recognized shapes of the objects.
An eleventh aspect of this invention is based on the second aspect thereof, and provides an apparatus wherein the object recognizing means comprises means for detecting speeds of the objects relative to the vehicle, means for detecting a speed of the vehicle, and means for determining whether the objects are moving or stationary in response to the detected relative speeds of the objects and the detected speed of the vehicle, and wherein the delineator-group determining means comprises means for determining ones among the stationary objects to be objects composing a delineator group.
A twelfth aspect of this invention is based on the second aspect thereof, and provides an apparatus wherein the detected height-wise positions of the objects comprise detected height-wise angles of the objects.
A thirteenth aspect of this invention provides a recording medium storing a program for controlling a computer operating as the object recognizing means, the delineator-group determining means, the on-road-surface delineator-group determining means, and the non-delineator determining means in the apparatus of the second aspect of this invention.